The manufacture of tubular bags on forming, filling and sealing machines is known for example from U.S. Pat. No. 4,391,081. The rotating friction belts which rest on a fill pipe pull the foil sheet supplied by a roller over a forming shoulder, with the initially flat foil being formed into a tube. The longitudinal seam is formed by sealing or welding of the overlapping edges. The forming shoulder has a fill pipe so that the goods to be packaged can be filled from above through the fill pipe into the tube. The bottom seam and at the same time the top seam of the preceding bag are created below the fill pipe by means of a cross-sealing station, with the two bags being separated from one another by means of a separating knife. The cross-sealing jaws, which lie transversely with respect to the direction of movement of the bag material, are here moved cyclically in one plane in order to be able to move the filled bag on downwardly after sealing.
A tubular bagging machine operating in this manner has become known from U.S. Pat. No. 4,815,253 which shows a device for the manufacture of upstanding bags. The sidewalls are folded inwardly below and above the sealing jaws shortly before the sealing by means of side-fold-forming means. The bag is moved downwardly after the sealing has taken place, with the bag being one more time shaped into a rectangular shape in a forming chamber consisting of two oppositely lying U-shaped elements prior to its top seam being formed and prior to the separation from the next following bag taking place.
Part of the state of the art is also to support the rectangular shape of the bag to be manufactured such that the fill pipe itself has, at least in the lower area, a rectangular cross section. However, it is also known to design the entire pipe rectangularly, with the forming shoulder changing the flat sheet into a rectangular tube.
It is disadvantageous in these intermittently operating packaging machines that, based on the standstill times of the cross-sealing jaw movement and of the unwinding foil, an upper limit exists for the machine performance. In particular, and due to the very fast foil acceleration, the frictional resistance between foil and friction belt is no longer guaranteed so that, due to slippage, the adjusted bag length can no longer be achieved.
In order to overcome the disadvantage of the intermittent tubular bagging machine, a continuously operating device is described in EP-PS 226 693. In contrast to the preceding devices, the cover material is continuously removed from the roller, is formed into a tube and is fed to the cross-sealing station. The longitudinal sealing task is also done continuously. The sealing jaws of the cross-sealing station describe in this case an essentially circular path, with significantly faster machine performances being possible due to the elimination of the standstill times of the jaw movement. Due to the linear movement of the control cam and of the movable arrangement of the cross-sealing jaw carrier, a sealing/welding path results over which the sealing jaws travel synchronously with the foil by a suitable driving control. Only so-called flat bags can be produced with this tubular bagging machine.
The closest state of the art is DE-OS 40 05 078. This reference shows a block base station following the cross-sealing station, which block base station has side-fold-forming tools which are horizontally movably supported. The movement of the tools is controlled through a cam directly associated with the tools. It can be disadvantageous in this known device that the cam cannot be sufficiently synchronized in its rotary speed with the movement of the cross-sealing jaws and the foil tube in order to control the horizontal movement of the side-fold-forming tools. In particular, and in the case of shorter cycle times and faster production speeds, considerable problems can therefore result.